No rain, but marine layer may obscure fireworks

Since weather records began in San Diego in 1850, there has never been measurable rain on July 4. That 159-year streak isn't threatened today.

But good visibility for some county fireworks shows tonight might be.

“It won't rain, but I can't guarantee anything about fog,” National Weather Service meteorologist Stefanie Sullivan said. “It really depends on when the marine layer decides to come back.”

Inland areas should be clear, at least until after the fireworks are over, Sullivan said. Near the coast, morning fog and low clouds could last into the afternoon, then creep back before the typical 9 p.m. fireworks hour.

There's not much fireworks operators can do about low clouds, said Julie Heckman, executive director of the American Pyrotechnics Association. The pyrotechnicians' only solutions are to lower the angle of the fireworks or move barges or launch points to increase visibility.

Most locals have never had to deal with July 4 rain, but it is usually not a problem at fireworks shows.

“Frequently, they will go on, rain or shine, as long as the wind is not a factor,” Heckman said. “The past two years, it's rained in New York for the Macy's show. It doesn't deter the crowd. They bring umbrellas.”

Wind is the big worry for fireworks operators. Shows are postponed if there's a danger debris could be blown over crowds, Heckman said.

Last year, storms in the Midwest postponed several shows, but today, the weather nationwide is shaping up well for fireworks displays, Heckman said.

July 4 is one of 11 days in San Diego's history when measurable rain has never been recorded. The other days are June 30; July 9, 12, 13, 19 and 24; Aug. 22, 23 and 24; and Sept. 2.